The plant hormone indoleacetic acid induces invasive growth in Saccharomyces cerevisiae

Abstract

Fungi must recognize plant-specific signals to initiate subsequent morphogenetic events such as filamentation that lead to infection. Here we show that the plant hormone indoleacetic acid (IAA) induces adhesion and filamentation of Saccharomyces cerevisiae. Genome expression profiling of cells treated with IAA identified Yap1, a fungal specific transcription factor, as a key mediator of this response. Strains lacking YAP1 (yap1-1) are hypersensitive to growth on IAA because they accumulate more IAA than can wild type. Members of a family of transporters the amino acid͞ auxin:proton symport permeases with homology to AUX1, a putative IAA transporter from plants, are up-regulated in the yap1-1 mutant. Deletion of any one of these transporters makes yap1-1 mutants more resistant to IAA by decreasing its uptake. The permease mutants are defective in IAA perception and filamentation. The ability of a fungus to perceive a plant hormone that causes it to differentiate into an invasive form has important implications for plant-pathogen interactions.

Indole-3-acetic acid: A widespread physiological code in interactions of fungi with other organisms

“…IAA is different from previously described signaling factors because its effects appear to cross species barriers. Prusty et al 13 reported that IAA promoted the growth of filamentous forms of Saccharomyces cerevisiae and promoted the invasion of the yeast, which supports the role of IAA as a signaling molecule regulating yeast growth. In their radioactivity studies of 3 H-IAA, they proved that IAA is taken up by cells and there exists a transport system for IAA uptake.…”

“…Similarly, previous studies have reported that IAA inhibits the growth of plant-associated fungi. 13,25 Kulkarni et al 25 showed that IAA influenced the growth of the plant pathogen F. delphinoides. Exogenous IAA at low concentrations increased the growth of F. delphinoides, whereas at high concentrations, it reduced the growth of F. delphinoides.…”

“…The present study revealed vital roles of IAA in plant -fungal pathogen interactions. 13 The plant pathogenic fungus Col. gloeosporioides f. sp. aeschynomene is capable of utilizing exogenous Trp for IAA synthesis through IAM.…”

“…10,11 In addition, several studies have shown that IAA is a signaling molecule in microorganisms because it affects gene expression in several microorganisms. 12,13 IAA can have a major impact on interactions between IAA-producing organisms. The auxin acts as an effector molecule between IAA-producing bacteria and plants, and bacteria -bacteria interactions have been discussed in several reviews.…”

Gene silencing is an ancient means of producing multiple phenotypes from the same genotype

“…For example, the yeast FLO11 gene is induced by auxin, a plant hormone that is produced at plant wound sites [18]. When a population of S. cerevisiae is placed in conditions that induce FLO11 expression, a minority of cells retain an inactive locus.…”